Alarm system



Feb. 14, 1939. c. H. SIMS ALARM SYSTEM Filed Oct. 26, 193

HSP

INVENTOR. CHARLES H. SIMS ATTORNEY.

Patented Feb. 14, 1939 UNITED STATES PATENT OFFICE ALARM SYSTEM Application October 26,

12 Claims.

This invention relates in general to alarm signalling systems and more particularly to systems such as are used for transmitting fire, police, burglar, or other similar alarm calls, and the main object is to provide improved and simplified arrangements of the circuits and apparatus tending to economize in the cost and maintenance of the equipment.

Another object is to provide an alarm system in 10 which all the lines are under constant supervision for unstandard conditions thereon and in which either a legitimate alarm signal or a line trouble alarm signal may be instantly detected. Other objects and certain novel features in connection therewith will be apparent from the description and the accompanying drawing illustrating by means of the usual schematic circuit diagram 2. preferred embodiment of the invention.

An alarm signalling station is indicated in full 20 at A, it being understood that this is one of a plurality of similarly equipped stations in the system. Each station has an individual pair of line conductors extending to a central office where they terminate in the alarm receiving equipment B associated with that particular station. Also at the central office there is provided common control equipment C associated with all the equipment B, B, etc. The operators cord circuit D at the central ofiice is used for testing the lines and for talking purposes with any station. In the system illustrated it will be assumed that the equipment is to be used for making emergency calls from a subscribers premises to the police.

At each alarm station A there is a non-locking key K and a. handset telephone HS both connected to the line. This line is of the closed circuit type with current normally flowing over it in a path extending from ground through the winding of high resistance relay ID in the associated equipment B at the central office; locking contacts l3 and operated armature spring I I of alarm relay l9 which is normally held energized in this circuit; upper closed contacts of the telephone jack JK; line conductor 3; normally closed contacts and I of alarm key K; normally closed contacts of the handset switchhook SW; line conductor 4; lower closed contacts of the telephone jack JK; through the trouble lamp TL to battery. The lamp TL receives insufiicient current in this circuit to illuminate due to the resistance of alarm relay H] which, however, as stated does energize. The resistor 8 connected to ground and the line 4 has a resistance of 10, QQQ

1936, Serial No. 107,586

ohms and therefore has no efiect at this time. Its purpose will be explained hereinafter.

When an alarm is transmitted the subscriber momentarily presses the button or key on his premises. This action momentarily opens contacts 5 and l and also connects ground from contact spring 6 onto spring 5 and over the line conductor 3, resulting in the deenergization of alarm relay to which immediately deenergizes and restores its armatures, thereby opening its lock- 10 ing circuit at contact spring 13 so it cannot again energize when the key K is restored or repeatedly operated. At its contact springs 15 relay I!) connects ground from the closed contacts of the line trouble key LK to the winding of the common 15 signal relay 2 5. This relay upon operating closes a circuit'at its contacts for the gong G to audibly call the attention of the attendant at the central office that an alarm has been received. At contacts l6 alarm relay Ml closes the circuit from ground on the trouble key LK to the alarm lamp AL which illuminates and thereby indicates to the attendant that the station A has initiated the alarm. As a further result of the deenergization of alarm relay it] it closes a circuit at its contacts I4 for slow acting relay 2t which slowly energizes and after a time opens its contacts 2|. Before this occurs, however, the ground at contacts I4 is extended over contacts 2! through the winding of magnet TR to battery. This magnet TB is individual to the station A and may be in the form of any well known printing or recording magnet wherein its energization operates an armature to either print or mark the moving tape 'I'P controlled in accordance with time mechanism, to make a permanent record at the central office of the station which sent in the alarm and also the time it was received. Relay 2!) upon fully energizing opens the circuit of magnet TR at its contacts 2! and remains operated under control of alarm relay 10. The alarm signal has now been transmitted and the attendant at the central office is made aware of it by the illumination of alarm lamp AL, operation of gong G, and the marking on the recording tape 'I'P, as pointed out.

After having received an alarm signal from a station such as A the central office attendant may require additional information or the person at the station may wish to further advise him. The attendant in this case takes up the plug PL of her cord circuit D and inserts it into the telephone jack JK associated with the station sending in the alarm. This connects the attendants handset telephone HSP through the closed contacts of key TK to the plug and jack contacts and the line conductors 3 and 4. At the station the removal of the handset telephone HS from the switchhook SW opens the switchhook contacts and connects the handset directly in circuit with the contacts 5 and 1 of alarm key K and the line conductors 3 and 4. Conversation can now take place with the talking potential supplied to both handset telephones through the windings of impedance coil 36.

To restore the equipment after it has been operated and also to check whether the alarm is a legitimate one and not caused by trouble on the line, the attendant at the central office momentarily operates the common reset key R thereby closing contacts 23 and connecting battery potential through a low resistance, through the new closed contacts I2 and I3 of alarm relay I0 and the winding of that relay to ground. As a result alarm relay I0 is again energized and maintained operated over its locking contacts H and I3 and over the line conductors 3 and 4 through the station A and in series with the lamp TL. At contacts M the circuit of relay 2B is opened, at contacts IS the circuit of signal relay 25 is opened to silence the gong G, and at contacts IS the energizing circuit of alarm lamp AL is disconnected. The equipment is now at normal again ready to receive other alarm signals. After receiving an alarm signal the attendant may operate the key AK in her cord circuit D and thereby connect her handset telephone I-ISP to the police trunk and provide the necessary instructions regarding the location of the alarm. The key AK disconnects the lower winding of impedance 36, as the talking battery in this instance is fed over the trunk line from the police exchange equipment.

Assume now that an accidental ground occurred somewhere along the line conductors 3 and 4 extending from the station to the ofiice or anywhere within the station or the ofiice; the foreign ground potential passes over the line conductors and results in the direct illumination of the trouble lamp TL to call the attendants attention to the trouble. As a further result alarm relay l0 deenergizes and by restoring its armature springs effects the registration of the trouble on the time recorder magnet, sounds the gong G, and illuminates the alarm lamp AL. The attendant then operates the line trouble key LK which at its normally open contacts connects direct ground potential to the trouble lamp TL to maintain it illuminated and at the normally closed contacts of the key disconnects the ground from the circuit of alarm lamp AL to extinguish it and also to restore relay 25 to silence the gong G. The circuits remain in this condition until the trouble has been cleared up after which the trouble key LK is restored and the reset key R, operated to energize relay l0 over the line circuit in series with lamp TL. From the foregoing it will be apparent that a momentary ground such as applied by the alarm key will initiate an alarm signal, while a permanent ground will result in a trouble alarm signal being transmitted.

In case the normally closed line circuit is accidentally opened but not grounded, relay in deenergizes and operates the alarm lamp AL, gong G, and also registers the signal on the magnet TR. The attendant will not be aware that this is a case of trouble and not a legitimate alarm signal until the reset key R is operated momentarily when he will observe that the alarm lamp AL will remain illuminated instead of g g out.

This is due to the fact that relay I!) cannot again remain energized over the line loop circuit after it is initially energized by the reset key R. The attendant thereupon operates the line trouble key LK to light the trouble lamp TL until the trouble is cleared.

Should it occur that the line conductors 3 and 4 be short circuited this would not automatically reveal itself as a source of trouble at the central office, because the contact springs 5 and I at the key K are normally closed. A regular alarm can, however, be transmitted to the central office because the ground on contact spring 6 is extended over both line conductors resulting in the illumination of trouble lamp TL and the short-circuiting of alarm relay ID to bring in the alarm signal, as pointed out. The illumination of trouble lamp TL indicates a case of trouble on the line and the attendant proceeds to test the line in the manner to be hereinafter pointed out.

The attendant as part of his duties will as a matter of routine periodically test the alarm receiving equipment B and for this purpose he is provided with the test key T. This key is conveniently made common to not more than five alarm lines so that the five equipments can be tested and observed simultaneously. Operation of test key T connects direct ground potential through its contacts 22 to armature l I and one side of the winding of alarm relay l0, thereby short-circuiting the same and deenergizing it to bring in the regular alarm signals, the same as if a regular alarm had been received. In addition the same ground potential from test key T extends over the line conductor and as the resistance of relay i0 is no longer included in this circuit the trouble lamp TL is illuminated. To restore the equipment to normal again the reset key R is actuated to operate relay ID as has been previously pointed out. This constitutes a test of the operativeness of the alarm equipment.

When a case of trouble has occurred on an alarm line the attendant, as has-been pointed out, operates the line trouble key LK which maintains trouble lamp TL illuminated and disconnects the regular alarm signals AL and G. The line in trouble is now prepared for further accurate testing by the attendant who first takes the cord circuit into use by inserting plug PL into the jack JK of the line and thereby cause the jack springs to disconnect the alarm receiving equipment B from the line. The test key TK is then operated to disconnect the attendants headset HSP and the impedance 30. The approximate normal line resistance of the alarm lines has been predetermined with the provision of the high resistance 8 connected to ground at each alarm station and accurate tests of the line conditions may be made by the voltmeter in the cord circuit D. The testing means comprises the 48-volt exchange battery, the voltmeter having a scale reading up to 100 volts and an internal resistance of 100,000 ohms, and the keys VK, NK, and PK. In measuring the resistance of an alarm line the well known formula is used whereby the line resistancev in ohms is equal to the product of the voltmeter resistance winding and the quotient obtained by dividing the difference between the voltage of the exchange battery and the voltmeter reading by that reading as expressed by the formula:

in which X is the line resistance to be measured,

E the exchange battery voltage, E the voltmeter reading, and R the resistance of the voltmeter. Tests are made for permanent grounds, open circuiting and foreign potential.

To test for the presence of ground potential on the positive line conductor 4 the key PK is held operated and thereby connects the negative battery potential from the closed contacts of key VK through the voltmeter, lower contacts of operated key TE and out over the line conductor 4, and through high resistance 8 to ground. The deflection of the voltmeter needle indicates the voltage drop on the line conductor 4 and by applying the formula as pointed out, the line resistance to ground may be obtained. If there is no deflection an open circuit in the line conductor 4 or a ground return is indicated. The same test is made to the negative line conductor 3, but in this case the key NK is operated instead of key PK.

In the case of a short circuit across the line conductors 3 and 4 the deflection of the voltmeter needle will indicate this because of the reduction of the predetermined known resistance of the line circuit through the high resistance 8 to ground.

Another test is made for the presence of a foreign potential on the line conductors. To make this test the key VK is operated and then the key PK. Ground is thereby connected through resistance I1 and the now closed contacts of key VK to the positive terminal of the voltmeter. The negative terminal is connected through operated contacts of key VK, PK, and TK to the line conductor 4. Deflection of the voltmeter needle indicates a grounded negative potential on the positive line conductor 4 and if the deflection of the needle is ofi the scale a grounded positive potential is indicated. The same test is made to the negative line conductor 3 but in this instance the key NK is operated instead of key PK. The removal of plug PL from the jack JK and restoration of key LK places the circuits again in normal condition provided, of course, that the line trouble has been cleared The invention having been described, what is considered to be new and is desired to be protected by Letters Patent will be set forth in the following claims:

What is claimed is:

1. In an alarm system, an alarm station, a central office, a line circuit extending between said station and said office and comprising a pair of line conductors, a key at said alarm station connected to said line conductors, a relay at said central oflice connected to one of said line conductors, a trouble signal connected to the other of said line conductors, means responsive to the operation of said key for operating said relay but not said trouble signal, and an alarm signal operative in response to the operation of said relay.

2. In an alarm system, an alarm station, a pair of line conductors extending to said alarm station, a key at said station connected to said line conductors, a relay at which one of said line conductors terminates, a trouble signal at which the other of said line conductors terminates, means for normally energizing said relay over a series circuit including said line conductors, said key and said trouble signal, means responsive to the operation of said key for opening the line conductors to deenergize said relay, and an alarm signal operated in response to the deenergization of said relay.

3. In an alarm system, an alarm station, a pair of line conductors extending to said station, a trouble signal and an alarm relay at which said line conductors respectively terminate, a key at said station connected to said line conductors, said relay being normally energized over a series circuit including said key, said alarm relay, said conductors and said trouble signal, said alarm relay being operated when energized over said series circuit, said trouble signal remaining inactive when energized over said circuit, means responsive to the operation of said key for interrupting said normally closed series circuit to deenergize said alarm relay, an alarm signal operated in response to the deenergization of said alarm relay, and means for reoperating said alarm relay over a circuit excluding said line conductors.

4. In an alarm system, an alarm key, an alarm relay and a trouble signal, a normally closed line circuit including said alarm key, said alarm relay and said trouble signal all connected in series, locking contacts in said alarm relay through which it is normally held energized over the line circuit, means responsive to the operation of said alarm key for opening said line circuit to cause the deenergization of said alarm relay and the opening of said locking contacts, an alarm signal operated in response to the deenergization of said alarm relay, and means for reenergizing said alarm relay over a circuit independently of said line circuit and including said locking contacts.

5. In an alarm system, a normally closed line circuit, an alarm station including thereat an alarm key connected to said line circuit, a trouble signal and an alarm relay connected in series and included in said line circuit, said alarm relay normally being operated when energized over said circuit, said trouble signal remaining inactive when energized over said circuit, means controlled by said alarm key for momentarily opening said line circuit to deenergize said alarm relay, an alarm signal operated in response to the deenergization of said alarm relay, and means operative when a fault occurs in said line circuit for deenergizing said line relay and for operating said trouble signal.

6. In an alarm system, a line circuit, an alarm relay and a trouble signal connected in series and included in said line circuit, said alarm relay normally energized over said line circuit, said alarm signal remaining inactive when energized over said circuit, an alarm key for opening said line circuit to deenergize said alarm relaywhen an alarm is transmitted, an alarm signal operated in response to the deenergization of said alarm relay, said alarm key also being operative to ground said line circuit to deenergize said alarm relay and operate said trouble signal in case the line is short-circuited at the time an alarm is transmitted, said alarm relay being automatically deenergized in case the line circuit is opened or grounded, means for reoperating said alarm relay after an alarm has been transmitted, said alarm relay failing to remain operated in case the line is grounded or open, and means for operating said trouble signal to indicate the case of trouble on the line until it is corrected and for disconnecting said alarm signal.

7. In an alarm system, a line circuit, an alarm relay including a set of locking contacts connected in said circuit, means for normally energizing said alarm relay over said line circuit, an alarm key included in said line circuit for v of said alarm and operative to reenergize said trouble signal being operative transmitting an alarm, means responsive to the operation of said alarm key for deenergizing'said alarm relay, means responsive to the deenergization of the alarm relay for giving an indication for opening said locking contacts, a reset key connected to said locking contacts, the operation of said reset key being eiTective to reenergize said alarm relay through said locking contacts over a circuit independent of said line circuit, and a testing key connected to said locking contacts, said testing key being operative to deenergize said alarm relay, thereby to simulate the sending of an alarm independent of said line circuit.

8. In an alarm system, a line circuit, an alarm relay, an alarm signal controlled by said alarm relay, a trouble signal connected in series with said alarm relay and included in said line cir-. cuit, said alarm relay being operated when energized over said series circuit, said trouble signal remaining inactive when energized over said circuit, an alarm key in said line circuit operative to deenergize said alarm relay, thereby to cause the operation of said alarm signal, a reset-key alarm relay, said when said line circuit is grounded, said alarm relay being deenergized when the said line circuit is grounded, and a line trouble key operative to maintain said trouble signal operated and to disconnect said alarm signal until the ground is removed from said line circuit.

9. In an alarm system, a line circuit, an alarm relay normally energized over said line circuit,

means for transmitting an alarm by opening said line circuit to deenergize said alarm relay, an alarm signal operated in response to the deenergization of said alarm relay, a slow acting relay operated in response to the deenergization of said alarm relay, registering means for record ing an alarm, and means controlled jointly by said slow acting relay and said alarm relay for operating said registering means.

10. In an alarm system, a line circuit, a line relay normally energized over said line circuit,

means responsive tothe transmission of an alarm over said line circuit for deenergizingsaid line,

relay to givean indication of said alarm, a slowacting relay operated in response to the deenergization of said alarm relay, registration means for recording the alarm transmitted, and a series circuit for operating said registration means extending through contacts of said alarm and slowacting relays, said circuit being closed in response to the deenergization of said alarm relay and before said slow-acting relay fully energizes.

11. In an alarm-system, a central oflice; a trouble signal, an alarm relay and an alarm signal all located at said oflice; said alarm signal being operative in response to, the operation of said alarm relay; an alarm station; a switch at said station; and circuits interconnecting said trouble signal, said alarm relay, said alarm signal and said switch; said circuits being so connected and arranged that said alarm signal is normally inactive and is operated in response to the operation of said key, said trouble signal is normally partially energized and remains only partially energized upon operation of said key, and said trouble signal operates upon the occurrence of a fault in said circuits.

12. An alarm system, an alarm station, a central ofiice, a pair of line conductors extending between said central oflice and said station, a relay and a trouble signal at said olfice, a key at said station, said relay and said signal normally being energizedover a circuit including said line conductors, saidkey, said relay and said signal, said relay being operated when energized over said series circuit, said trouble signal remaining inactive when energized over said circuit and being operative when a fault occurs in said circuit, means responsible to the operation of said key for interrupting said circuit to deenergize said relay, an alarm signal at said office operated in response to the deenergization of said alarm relay, and operator control means at said ofiice for reenergizing said relay.

CHARLES H. SIMS. 

